The present invention relates to coding information using a CMI code and more particularly the coding of multiplexed digital information organized for example in frames.
The CMI code is well known. Such a code for example is described in the notice G 703 pages 55 to 57 of the CCITT such as reshaped in Geneva in 1980. The CMI code is a two level code without zero return of the signal. A binary 0 at the input is coded into a signal with level A.sub.1 and A.sub.2 (respectively low level and high level) in each half period (time T/2). A binary "1" at the input is coded into a signal of level A.sub.1 or A.sub.2 over a period, this level alternating for successive binary "1"s. The CMI code may be expressed more simply by saying that a binary "1" is coded 00 and 11 alternately and a binary "0" is coded 01.
However, when the binary train of information results from the multiplexing of a plurality of signals organized in frames, for recognizing these signals it is necessary to provide a frame locking word. Now, the insertion of such a word may disturb the statistics of the code itself.